1. Technical Field
The present invention relates to a photodetection device including a light guiding member for guiding incident light to a photodetection element.
2. Related Art
Conventionally, there has been known a photodetection device provided in a vehicle in order to automatically control lamps and an air conditioner of the vehicle. This photodetection device detects illuminance of light and solar radiation entering a vehicle interior by a photodetection element to control the lamps and the air conditioner, based on the detection result, as disclosed in, for example, Japanese Unexamined Patent Publications Nos. 2011-226946, 2012-183886 and 2010-276421, and Japanese Patent Nos. 3268888 and 3218558.
As a specific structure of the photodetection device, a light passing part that passes the light is provided on a light source side of the photodetection element. For example, the light passing part is made of an optical element such as a lens, a prism and the like in JP 2011-226946 A, JP 3268888 B1 and JP 3218558 B1, and the light passing part is made of an opening portion of a housing or the like in JP 2012-183886 A and JP 2010-276421 A. In JP 2011-226946 A, the photodetection element is arranged immediately under the light passing part (lens) to detect light passing the light passing part by the photodetection element.
For example, in order to control an air conditioner to properly set a temperature in a vehicle interior, not only brightness around a vehicle needs to be detected but also light directly shining on a user on a vehicle needs to be detected. Thus, an amount of light (an infrared amount and the like) from a predetermined oblique direction to the vehicle interior needs to be detected. Moreover, in order to control lamps of the vehicle, when the brightness around the vehicle is detected as well, the light from the predetermined oblique direction to the vehicle needs to be detected to perform the control more matching brightness that a driver feels.
Consequently, in JP 2012-183886 A, a light guide made of transparent or colored resin or glass is provided between the light passing part (a notch portion and a cutout portion) and the photodetection element. Front light passing through the notch portion is transmitted through a first light guide to be guided to a first photodetection element. Moreover, after upper light passing through the notch portion is caused to enter from an incident surface of the first light guide, the upper light is totally reflected at a boundary surface to change an optical path, and is guided to the first photodetection element. Furthermore, ambient light passing through the cutout portion is condensed at a condensing lens part provided in a second light guide to be guided to a second photodetection element.
In JP 2010-276421 A, a prism in which an incident surface is divided into three inclined surfaces is provided between the light passing part (opening portion) and three photodetection elements. Front light of light passing through the light passing part is guided to the first photodetection element by the first inclined surface, upper left light is guided to the second photodetection element by the second inclined surface, and upper right light is guided to the third photodetection element by the third inclined surface.
In JP 3268888 B1, a surface on the light source side of the optical element constituting the light passing part is convex, and a surface on a photodetection element side is an assemblage of prism surfaces. A center of these prism surfaces has a spindle shape opened on the photodetection element side with a point on an optical axis of the optical element as an origin. This brings about predetermined output characteristics with respect to incident angles in a gamut from a vertical direction to a horizontal direction.
In JP 3218558 B1, a conical lens part, a concave lens part, and a convex lens part are provided in a surface on the photodetection element side of the lens constituting the light passing part. The conical lens part shields light from direct above and transmits oblique light. Moreover, the concave lens part guides oblique to horizontal light to the photodetection element, and the convex lens part guides oblique light in a predetermined range to the photodetection element.
In JP 2012-202683 A, there has been disclosed a technique of pasting a transmission attenuation sheet on a portion of a lens to thereby make a light transmission amount of the relevant portion different from that of the other portion.